Linear electric motor propulsion system

ABSTRACT

A linear motor propulsion system for vehicles adapted to travel along a fixed roadway comprising primary and secondary motor elements, one of which is carried by the vehicle and the other of which is disposed in a discontinuous fashion along the roadway. A constant thrust profile is achieved by arranging the length and spacing of the elements such that a constant area of projected surface coextension exists between the elements irrespective of the vehicle position along the roadway.

uulwu mates ratent Donlon et al. 1 Jan. 23, 1973 541 LINEAR ELECTRICMOTOR 2,640,955 6/1953 Fisher ..318/135 PROPULSION SYSTEM PrimaryExaminer-Gerald M. Forlenza [75] Inventors: Richard H. Donlon,Littleton; Wil- Assistant Examiner ceorge Libman 2*? Hamllton Auroraboth of Attorney-McGlynn, Reising, Milton & Ethington [73] Assignee:Transportation Technology, Inc.,

Denver, Colo. [57] ABSTRACT [22] Filed: Feb. 23, 1971 A linear motorpropulsion system for vehicles adapted to travel along a fixed roadwaycomprising primary [211 App]' and secondary motor elements, one of whichis carried by the vehicle and the other of which is disposed in a [52][1.8. CI ..l04/148 LM, 310/13 discontinuous fashion along the roadway. Aconstant [51] Int. Cl. ..B60l 9/16, B601 11/00, B601 13/00 thrustprofile is achieved by arranging the length and [58] Field ofSearch...l04/l48 LM, 148 MS; 310/12, spacing of the elements such that aconstant area of 310/13; 318/135 projected surface coextension existsbetween the elements irrespective of the vehicle position along the [56]References Cited roadway.

UNITED STATES PATENTS 8 Claims, 3 Drawing Figures 3,233,559 2/1966 Smithet al ..l04/148 LM PATENTEDJANZS I973 3.712.240

4L-- -JL ATTORNEYS LINEAR ELECTRIC MOTOR PROPULSION SYSTEM Thisinvention relates to vehicular propulsion by linear electric motors andparticularly to the achievement of a substantially constant thrustprofile using discontinuous motor elements.

It is now well known that the linear induction motor may be employed forthe propulsion of vehicles along fixed roadways. The initialapplications of linear induction motors to vehicular propulsion were inrail vehicles similar to conventional trolley or train cars. Morerecently linear electric motors have been proposed for the propulsion ofvehicles which are supported relative to a fixed roadway by means of alow-pressure air cushion which reduces friction between the vehicle andthe roadway to the point of negligibility.

As is well known to those familiar with electric motors, the linearelectric motor comprises a field producing element, normally called aprimary, and a field reactive element, normally called a secondary. Itis customary for one or the other of these elements to bediscontinuously arrayed along .the roadway to save material andinstallation expense. In such a design the propelled vehicle actuallyexperiences an intermittent thrust profile, a thrust pulse being appliedas the vehicle passes over each of the intermittent motor elements. Thisintermittent thrust profile may be transmitted through the motorcarriage to the vehicle frame and be disturbing in varying amounts tothe passengers. Some degree of mitigation can be accomplished byresilient motor mounting as well as by arranging the intermittentelements closely together so that at speed the thrust pulses are closelyspaced in time.

In accordance with the present invention the thrust profile of a linearelectric motor propulsion system having at least one intermittent motorelement is caused to be substantially constant by designing the lengthof one element and the spacing between the other discontinuous elementsto be such that the area of motor elements overlying one another, thatis, being in projected surface coextension, is constant irrespective ofthe position of the vehicle relative to the roadway.

ln the preferred form, the element disposed on the vehicle, eitherprimary or secondary, is of such length as to be equal to the spacingbetween the centerlines of two of the discontinuous element portions inthe roadway. Accordingly, movement of the vehicle along the roadwaycauses a constant area of projected surface coextension between thevehicle mounted and roadway motor elements. Since the thrust experiencedby the vehicle is a function of the overlying motor areas and theseoverlying motor areas are constant with respect to time at least over aportion of the roadway, the vehicle experiences a relatively constantthrust profile. It is to be understood, of course, that the spacingbetween the discontinuous motor elements may be varied over differentportions of any given roadway and, therefore, that the principles of thesubject invention may be applied selectively to a given portion of aroadway.

The various features and advantages of the invention will become moreapparent from a reading of the following specification which describesillustrative embodiments of the invention in detail. The specificationis to be taken with the accompanying drawing of which:

FIG. 1 is a schematic view of a first embodiment of the invention;

way 12, while not described or illustrated in detail, is

preferably of the guideway type having at least two angled supportsurfaces to provide both vertical and lateral support for the vehicle10. Such roadways are known in the prior art.

Vehicle 10 is propelled and preferably braked by means of a linearelectric motor having a field producing primary element 16 of thedistributed winding type mounted on the vehicle so as to be adjacent butslightly spaced from the surface of the roadway l2. Alternating currentis supplied to the field winding of the primary element 16 through acontrol unit 18 which is preferably of the type employing rheostats andphase shifting circuitry subject to automatic or manual control. Theinput to control unit 18 is provided by a brush contact 20 which isdisposed on the exterior of the vehicle 10 and which rides on a thirdrail conductor 22 which extends continuously along the roadway 12. Othertypes of power input devices may, of course, be employed, as forexamples, a trolley or self-contained power source.

The primary motor element 16 provides thrust for the vehicle 10 bycooperating with the field reactive secondary element 24 which isdistributed along the roadway 12 in discontinuous portion a, b, and c.The secondary portions 24a, 24b, and 24c'may, for example, be aluminumplates permanently disposed in a concrete or asphalt base and, over theportion of the roadway 12 shown in FIG. 1, are placed at regularintervals of equal length such that a constant distance exists betweenthe center lines of the secondary element portions.

As illustrated in FIG. 1, the length of the field producing primary 16is equal to the distance between the centerlines of the adjacent fieldreactive secondary element portions 24a and 24b. Accordingly, as thevehicle 10 advances to the left the primary element 16 shades more ofthe secondary element portion 24a and less of the secondary elementportion 24b. The reverse is, of course, true as vehicle 10 advances tothe right as shown in FIG. 1. As a result the projected surfacecoextension or shaded area between the primary and secondary elements 16and 24, respectively, is constant as the vehicle 10 progresses along theroadway 12. This constant shaded area gives rise to a constant thrustwith little or no discontinuity or intermittent character even thoughthe secondary 24 is discontinuously placed along the roadway 12. Thesame effect is achieved if the primary element 16 is made equal inlength to the distance between centerlines of any two regularly spacedportions of element 24, whether such portions be adjacent or separatedby one or more other portions. The linear electric motor is preferablyoperated in the speed range to the right of point 36 in the diagram ofFIG. 3. In this range it can be seen that a decrease in speed caused byincreased load on the motor moves the motor operating characteristicupwardly on the trust curve producing an immediate correction and arestoration of normal operating speed.

As will be apparent to those skilled in the motor art, the primaryelement 16 and secondary element 24 may be interchanged in relativeposition as shown in FIG. 1. The secondary may accordingly be placed onthe vehicle in place of the primary element 16 and the roadway 12 may beequipped with a discontinuous series of field-producing primaryelements. This eliminates the need for the third rail conductor 22, anarrangement which may be preferably for short run operations. Theaforementioned constant thrust profile is again achieved by fabricatingthe vehicle mounted secondary to be of such length as to be equal to thespacing between centerlines of regularly spaced roadway mounted primaryelements.

Referring now to FIG. 2, another embodiment of the invention is shownwherein the vehicle 26 is adapted to carry a two-part secondary element34 having portions a and b and the roadway 28 is provided with adiscontinuous primary element 32 having portions a, b, and c.

.In FIG. 2, the vehicle 26, which is illustrated as being larger thanthe vehicle 10 of FIG. 1, is supported relative to a fixed guideway-typeroadway 28 by means of the air pad 30. The field producing primaryelement portions 32a, 32b, and 32c are interconnected with analternating current power source, as indicated, and are of equal lengthand regular spacing. The secondary element portions 34a and 34b areagain aluminum plates of equal width, thickness, and length and arespaced such that the overall length of the element 34, including thespace between, is equal to the distance between centerlines of elementportions 32.

To achieve the constant thrust profile, previously described, theprimary element portion 32b is of such length as to be equal to thedistance between centerlines of the secondary elements 34a and 34b.Thus, as the vehicle 26 moves either left or right along the roadway 28a constant area of projected surface coextension as between the primaryand secondary elements 32 and 34, respectively, is achieved. Again, theprimary and secondary element identities in the arrangement of FIG. 2may be reversed; that is, the primary elements may be disposed on thevehicle in the two-part discontinuous fashion illustrated for thesecondary portions 34a and 34b and the illustrated primary element 32may be interchanged with aluminum plates to act as secondary elements.In such an arrangement, either a vehicle carried power generator or anexternal pickup arrangement is required.

Although the invention has been described as being applied exclusivelyto air-supported vehicles 10 and 26, it is to be understood that othertypes of support means such as steel wheels and rubber tires may beemployed,

the principles of electric motor propulsion being the same irrespectiveof the support means type. Moreover, the linear motors may be mountedsuch that the air gap between primary and secondary is vertical ratherthan horizontal as shown, or at some intermediate angle. Suchnonhorizontal motors may straddle a rail or coact with guideway wallelements. These modifications are not exhaustive of the possibilities.Therefore, the illustrative explanations given above are not to beconstrued as limiting the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a vehicular propulsion system: a vehicle adapted for travel over aroadway, a linear motor for propelling the vehicle and including fieldproducing and field reactive elements, one of said elements beingcarried by the vehicle and the other of said elements being disposed indiscontinuous portions along the roadway, said elements being maintainedin adjacent but spaced relation to produce a thrust on said vehicle inproportion to the projected area coextension of said elements, thelength of said one element and the spacing between said otherdiscontinuous element portions being such that the area of projectedsurface coextension between said elements and the thrust on said vehicleis constant irrespective of the position of the vehicle longitudinallyalong to the roadway as said vehicle travels over a length of roadwaywhich is great as compared to the length of said one element.

2. A system as defined in claim 1 wherein the length of said one elementis equal to the distance between the longitudinal centers ofdiscontinuous element portions.

3. A system as defined in claim 2 wherein the discontinuous elementportions are of equal length and spacmg.

4. A system as defined in claim 3 wherein the field reactive element isdisposed in said discontinuous portions along the roadway.

5. A system as defined in claim 4 including a power source disposedsubstantially continuously along the roadway and means carried by thevehicle for variably interconnecting the source to the field producingelement.

6. A system as defined in claim 4 including air support means on thevehicle for substantially frictionlessly supporting the vehicle relativeto the roadway.

7. A system as defined in claim 2 wherein the field reactive element isdisposed on the vehicle.

8. A system as defined in claim 7 including air support means on thevehicle for supporting the vehicle relative to the roadway.

1. In a vehicular propulsion system: a vehicle adapted for travel over aroadway, a linear motor for propelling the vehicle and including fieldproducing and field reactive elements, one of said elements beingcarried by the vehicle and the other of said elements being disposed indiscontinuous portions along the roadway, said elements being maintainedin adjacent but spaced relation to produce a thrust on said vehicle inproportion to the projected area coextension of said elements, thelength of said one element and the spacing between said otherdiscontinuous element portions being such that the area of projectedsurface coextension between said elements and the thrust on said vehiclEis constant irrespective of the position of the vehicle longitudinallyalong to the roadway as said vehicle travels over a length of roadwaywhich is great as compared to the length of said one element.
 2. Asystem as defined in claim 1 wherein the length of said one element isequal to the distance between the longitudinal centers of discontinuouselement portions.
 3. A system as defined in claim 2 wherein thediscontinuous element portions are of equal length and spacing.
 4. Asystem as defined in claim 3 wherein the field reactive element isdisposed in said discontinuous portions along the roadway.
 5. A systemas defined in claim 4 including a power source disposed substantiallycontinuously along the roadway and means carried by the vehicle forvariably interconnecting the source to the field producing element.
 6. Asystem as defined in claim 4 including air support means on the vehiclefor substantially frictionlessly supporting the vehicle relative to theroadway.
 7. A system as defined in claim 2 wherein the field reactiveelement is disposed on the vehicle.
 8. A system as defined in claim 7including air support means on the vehicle for supporting the vehiclerelative to the roadway.